Fuel tanks have been provided to straddled vehicles such as motorcycles. In fuel tanks, a fuel filler port device has been provided that includes: a fuel filler guide tube that extends to inside of the fuel tank from a fuel filler port provided in the superior wall thereof, and into which the nozzle of a fuel filler gun is inserted; a flame arrester that covers the opening at the lower end of the fuel filler guide tube, and permits the flow of fuel from the nozzle to inside of the fuel tank; and a gun stopper positioned above the flame arrester and preventing contact between the nozzle inserted inside of the fuel filler guide tube and the flame arrester.
Patent Document 1 proposes a fuel filler port device provided with a cylindrical skirt at the circumference of the flame arrester, and in which vents are formed in the skirt and the fuel filler guide tube, respectively. With the fuel filler port device proposed in Patent Document 1, in a case where the fuel level inside of the fuel tank has risen to at least the lower end of the skirt accompanying fuel filling, the air in the upper portion of the fuel tank is discharged from the vents formed in the skirt and the vents formed in the fuel filler guide tube, whereby the flow of fuel to inside of the fuel tank is carried out smoothly. Then, when the fuel level reaches the level of the vents formed in the skirt or higher, the discharge of air in the upper portion of the fuel tank will be only from the vents formed in the fuel filler guide tube, and the fuel level will rise inside of the fuel filler guide tube. The fuel filler operator observing this situation will notice that fuel has filled the fuel tank.    Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2009-101854